1. Field of the Invention
This invention relates to a projection lens system for a projection type of television which is applicable to cameras, such as electronic cameras using charge coupled devices or image pickup devices as image recording media and cameras for use with silver films as image recording media.
2. Description of Related Art
Typically, projection lenses for television sets of the type having a liquid crystal screen have a need to employ a telecentric optical system therein in interrelation to a liquid crystal panel, an illumination system and a color composing optical system and/or to have a long back focal distance in order to incorporate the telecentric optical system therein. One of the projection lenses which satisfy these needs is known from, for example, Japanese Unexamined Patent Publication No. 63-81414. This prior art projection lens comprises a less number of lens elements than before and has a back focal distance longer as compared with its focal length, realizing a desired telecentric optical system.
Projection lens having a back focal distance longer as compared with its focal length are confronted with an large-sized external shape. While projection systems using a liquid crystal device throw a picture with distortion enhanced more than a pictures on an ordinary television screen or a printed picture, and hence have to kept distortion as less as possible, the prior art projection lens described in the above mentioned publication is still hard to have sufficiently corrected distortion.